With the autoradiographic technique and the Fink-Heimer method, we have been tracing connections in the cerebral hemispheres of the rhesus monkey and the squirrel monkey. Our long term goal in this project is to determine the areal and laminar site for termination of the callosal, associational and thalamic axon. Thus far we have demonstrated the distribution of the callosal system in the rat, squirrel monkey and chimpanzee and we have noted many similarities in this system in these mammals. We are currently tracing the associational connections within the squirrel monkey cerebrum pursuant to the goals described in the study.